A sea of green.

When thousands of Pittsburghers pack Downtown on Saturday for the annual St. Patrick’s Day parade in a sea of green, they’ll be part of a tradition 150 years in the making.

Though Pittsburgh’s parade halted for several years, particularly during blizzards, times of war, or when St. Patrick’s Day fell on a Sunday, this year’s parade will mark 150 years since the very first — a milestone worth celebrating, parade organizer Jan Griffith said.

“It’s not 150 consecutive years, but we’ll celebrate anything,” she said.

The parade has grown from humble roots into one of the largest in the nation and, at least according to one website, Pittsburgh is among the best places to celebrate the holiday.

This weekend, between 150,000 to 200,000 people are expected to watch as some 50,000 Pittsburghers march in the parade. The parade begins at 10 a.m. on Saturday, March 16 — here’s the full route. For those who can’t make it, WTAE will livestream the festivities.

A pipe band parades through Pittsburgh in 2018.

Looking back, the city’s first St. Patrick’s Day Parade, held on March 17, 1869, didn’t quite go as planned, as deliverymen unloading wagons impeded the procession of St. Patrick, according to the parade’s official history, compiled by Michael R. Murphy.

In 1871, the “Confederated Irishmen of Lawrenceville” marched through the rain wearing sashes reading “God Save Ireland,” per the parade’s website. In 1874, marchers traversed exhausting routes from the North Side to the South Side to Downtown — “they just marched for miles,” Griffith said.

During the 2018 parade, one lucky couple even stopped the show with their mid-parade engagement. Griffith hasn’t heard about any engagements planned for this year — not yet, anyway.

This fairytale chariot comes with shamrocks.

Courtesy of Ryan McArdle

When the parade steps off on Saturday, expect 190 groups to march along the parade route, including marching bands, pipers, drum corps, dancers, Irish wolfhounds, clowns, horse patrols, political officials, and the Rooney family with Steely McBeam.

“It’s one of the largest we’ve had so far,” Griffith said.

The parade committee strives to make sure it’s a family-friendly event, and a family festival will be held in Market Square from 10 a.m. until 2 p.m.